1. Field of the Invention
The present invention relates to a multi-cavity mold for use in an aluminum die cast molding or the like.
2. Description of the Related Art
In a multi-cavity mold, it is necessary to have the quality stabilized between products. As one of the causes of quality variation in the products, there is a difference in filling time of a molten metal between cavities for each of the products. Therefore, if the molten metal is filled simultaneously into the cavities of each of the products, the quality may be stabilized. In this point of view, there is the art that the cavities of each of the products are arranged substantially in the shape of a sector form with respect to a sleeve (see a patent reference 1).
Further, when the molten metal is filled into the sleeve, a portion of the molten metal which contacts a low temperature inner wall of the sleeve is rapidly cooled thereby forming a chill (quenching organization). At the same time, an oxide film is formed on a surface of the molten metal. These solidification layer and oxide film are mixed with a liquid molten metal so as to form a semi-solidified layer thereby giving rise to deterioration in liquidity and to deterioration in pressure transfer property. When a gate portion is filled with the semi-solidified metal, the run of the molten metal is inhibited so as to cause the poor run of the molten metal, and then the injection pressure is increased so as to produce the burr and to shorten the life of the mold. Further, this semi-solidified layer is greatly different in organization from other portion of the molten metal. Therefore, when an oxide substance and a broken chill each of which forms a portion of the semi-solidified layer are included in the product, quality deficiencies such as faulty in thickness by contamination of a foreign substance with respect to the casting product, separation of the chilled layer after machining of the casting product and the like may be developed. In this point of view, the art that a reservoir is provided around a flow divider for preventing penetration of the oxide substance and the broken chill into the product is publicly known (see patent references 2 and 3).
Patent reference 1: Japanese patent laid-open publication No. S64-34554A.
Patent reference 2: Japanese patent laid-open publication No. S63-144852A.
Patent reference 3: Japanese patent laid-open publication No. 2005-59044A.
In the multi-cavity mold, it is necessary to fill the molten metal uniformly and simultaneously into each of product forming sections. Moreover, it is necessary to prevent the penetration of the oxide substance and the broken chill into each of the products.
Further, in the case of mass production, a die temperature is low in an initial number of casting times (shots) and reaches a predetermined temperature by repeating shots several times, whereby the quality of the product is stabilized. In this case, the products before reaching the predetermined temperature are defective. However, because of the multi-cavity mold, the number of defective products becomes greater as the number of defective shots increases, so that it is desirable to reduce the number of such defective shots. Therefore, the present invention aims to make it possible to supply the molten metal of little impurities and good flowability so as to materialize the above mentioned various requirements.